1. Technical Field
The present invention relates to a piezoelectric motor which utilizes the oscillation of a piezoelectric body, a drive unit provided with a mechanism of the piezoelectric motor, an electronic part transfer apparatus, an electronic part inspection apparatus, a robot, and a printer.
2. Related Art
In the related art, an ultrasonic motor on which a piezoelectric actuator having a piezoelectric ceramics board and a pressing member is mounted as described in JP-A-2004-236493 is disclosed as a piezoelectric motor. The ultrasonic motor has a configuration in which the pressing member performs an oval motion by the oscillation of the piezoelectric ceramics board. The ultrasonic motor is configured to move a movable member (stage) in abutment with the pressing member along a guide rail by the oval motion of the pressing member. In this case, hardness H1 of an abutting portion of the pressing member and hardness H2 of an abutting portion of the movable member are preferably set to H1/H2=0.75 to 1.5, whereby abrasion at the abutting portions may effectively be restrained.
JP-A-2007-306799 discloses an ultrasonic actuator (piezoelectric motor) having a piezoelectric element and a driver configured to perform an oval motion by the oscillation of the piezoelectric element. The ultrasonic actuator has a configuration in which the abutting portion between the driver and the movable member is minimized in a relationship between the driver and the movable member which is driven by abutment with the driver, whereby the efficient driving of the movable member is enabled. In this configuration, when the driver and the movable member are formed of alumina, the alumina for the movable member having a hardness lower than that of the alumina for the driver is considered to be preferable.
However, the hardness of the pressing member and the movable member described in JP-A-2004-236493 is so-called plastic deformation hardness, and is expressed by Vickers hardness. In JP-A-2007-306799 as well, setting relating to the hardness of the driver and the movable member is performed although the term “plastic deformation hardness (Vickers hardness)” is not set forth. Here, in the piezoelectric motor such as the ultrasonic motor, there is a case where the abrasion caused by a sliding motion may not be restrained effectively only by the setting on the basis of the plastic deformation hardness, and the mechanism of abrasion in the piezoelectric motor is being clarified not to be affected only by the plastic deformation hardness. Therefore, there is a problem that effective restraint of the abrasion caused by the sliding motion is difficult only by setting the hardness on the basis of the plastic deformation hardness as described in JP-A-2004-236493 and JP-A-2007-306799.